1. Field of the Invention
Aspects of the present invention relate to a polymer electrolyte membrane fuel cell, and more particularly, to a fuel cell stack and manufacturing method thereof including a new sealing structure.
2. Description of the Related Art
Since fuel cells are pollution-free power sources, fuel cells have been spotlighted as next generation clean energy power generation systems. Fuel cells have advantages in that a power generation system using the fuel cell can be used as a self-generator for a large building, as a power supply for an electric vehicle, as a portable power supply, etc., and can use various fuels such as natural gas, city gas, naphtha, methanol, waste gas, etc. Types of fuel cells, which basically operate by the same principles, include phosphoric acid fuel cells, alkaline fuel cells, polymer electrolyte membrane fuel cells (PEMFC), direct methanol fuel cells, and solid oxide fuel cells, in accordance with types of electrolytes used in the fuel cell.
Since s polymer electrolyte membrane fuel cell (PEMFC) uses a polymer membrane as an electrolyte, the polymer electrolyte membrane has no risk of corrosion or evaporation due to the electrolyte and can obtain high current density per unit area. Moreover, since the polymer electrolyte membrane fuel cell has a high output characteristic and low operating temperature, as compared to other kinds of fuel cells, the polymer electrolyte membrane fuel cell has actively been developed as a portable power supply to supply power to a vehicle, a distributed power supply to supply power to a house or a public building, etc., and a small power supply to supply power to electronic equipment, etc.
The polymer electrolyte membrane fuel cell is typically manufactured in a stack structure by stacking a plurality of membrane electrode assemblies (MEAs), each constituted by an anode electrode, a cathode electrode and a polymer electrolyte membrane positioned between the anode electrode and the cathode electrode, wherein separators are interposed between the membrane electrode assemblies. In manufacturing the fuel cell stack, a sealant is inserted between the membrane electrode assembly and the separator to prevent the leakage of fuel or oxidant flowing through a channel installed in the separator and to prevent the influx of outside air.
In general, the fuel cell stack is sealed by discharging, hardening, and compressing (or discharging, compressing, then hardening) materials that have some elasticity, such as resin, etc., or by using an O-ring type gasket. However, performing the discharge, hardening, and compression of elastic materials has the disadvantages that it takes a long time to harden the materials and it is difficult to maintain uniform discharge state. If discharging and compressing are carried out before hardening, there are disadvantages that since the stack is assembled before the relatively thickly applied sealant material, which may be relatively thickly applied, is hardened, the parts of the stack may not be precisely and firmly seated in situ so that the membrane electrode assembly or the separator may be polluted by sealant that migrates from the sealing area. In particular, when the parts of the stack are polluted with sealant, the waste of the parts of the stack is increased. Also, sealing a fuel cell stack using an O-ring type of the gasket has the disadvantages that the design of the stack and the manufacturing process thereof are restricted by constraints on the manufacture of the gasket. Therefore, in the existing fuel cell stack a sealing method using an O-ring has the problems that cracks can occur in the parts of the fuel cell stack or between the parts of the fuel cell stack by outside impact because of the particular material or structure of the parts used in the fuel cell stack, so that leakage occurs.